Seminar at SMU Delhi

Krein's formula gives an expression for the trace of the difference of a function of a self-adjoint operator and its perturbation by the addition of a trace-class operator , while that due to Helton and Howe deals with the trace of the commutator of functions of a hyponormal operator and its adjoint . The impact of Krein's theorem on the derivation of the Helton-Howe formula will be discussed .